In the vehicle development and design stage, the evaluation of collision performance of a vehicle body is inevitable, and a vehicle maker builds a prototype vehicle and performs a collision test (collision experiment) to check that collision performance is ensured as desired and then proceeds to mass production. However, in a case where any member has insufficient strength, measures are taken to increase the strength of the member, and then a prototype vehicle needs to be build again to perform a collision test again. This process needs much development cost and time, which has a great influence on the development process.
In order to solve this problem, the collision performance testing of member units has been performed in the past. Basic members greatly influencing the collision performance of a vehicle have been already known in the art, and for example, in the case of side collision, a center pillar and a side sill are the most important members. If the performance evaluation of those members may be performed with the same conditions in a state where those members are mounted to an actual vehicle body (in a full vehicle state), the cost and time for manufacturing a prototype vehicle again may be saved.
However, in a case where 3-point bending test or the like is performed on each of those members separately, compared with the case a collision test is performed in a state where those members are mounted in an actual vehicle body, the support method of the member and the influence exerted by peripheral members may not be sufficiently reflected, and therefore the evaluation accuracy is too low to determine whether or not to adopt the member for an actual vehicle.
Meanwhile, a method of performing collision performance evaluation of vehicle members on a computer is widely used. For example, Patent Document 1 discloses a method of evaluating buckling characteristics of a center pillar during a collision by the dynamic explicit method using a computer aided engineering (CAE) model. The analysis using the CAE model in a full vehicle state is an effective collision performance evaluation method since the interaction between the member subject to the performance evaluation and other members may be accurately evaluated. However, the collision simulation in the full vehicle state is a very high load, and its execution needs a great deal of calculating ability and several days of calculating time. Therefore, it is difficult to perform the collision simulation a sufficient number of times. In addition, even if the calculating time is ensured, in the analysis using the CAE model, it is impossible to exactly reflect the work hardening occurring in a member fabricating process, thermal influence during welding, and a rupture phenomenon of a material. For this reason, to determine whether or not to adopt the member in an actual vehicle, the analysis using the CAE model even in a full vehicle analysis may not ensure sufficient reliability.
For those reasons, even though various technologies are being developed, it is still difficult to evaluate the collision performance of a vehicle member in an efficient and very accurate manner.